An efficient stereoselective and stereodivergent synthesis of (2R,3R)- and (2R,3S)-3-hydroxypipecolic acids

Asymmetric syntheses of (2R,3R) and (2R,3S)-3-hydroxypipecolic acids are reported featuring a key diastereoselective addition of Büchiʹs Grignard reagent to the chiral serinal l-5. Based on conformational analysis, a stereocontrolled reduction of piperidin-3-one (15) to cis 2,3-disubstituted piperidine (16) is also described.